Conventional domestic refrigerators are internally illuminated by a single light source, usually a conventional incandescent light bulb, contained within a transparent or translucent housing and located on one of the internal sides of the refrigerator. The light source is activated by a suitable electro-mechanical switching device on the opening of the door of the refrigerator. Such light sources tend to offer poor illumination due to their location within the refrigerator or the low wattage of the light bulb. Improved illumination by increasing the number of light sources reduces the capacity and increases the cost of the refrigerator. Additionally, such an increase in the number of the light sources within the refrigerator also increases the total heat energy dissipated. This increase in heat dissipation produces an undesirable temperature rise within the refrigerator which has to be compensated for by an increased refrigeration effect. The same occurs when a more intense single light source having a higher wattage is used instead of increasing the number of light sources. Furthermore, the continuous illumination of domestic refrigerators, for example where the refrigerator has a transparent door through which its contents can be viewed, is also not desirable given the amount of heat dissipated from the light sources or more intense light source.
The state of the art in respect of illuminated edge-lit display systems, as used in vertically mounted signs, is typified by EP-A 0549679. EP-A-0549679 addresses the problem of uneven illumination of an edge-lit system by applying a matrix of dots to two opposing surfaces of a transparent sheet which is edge-lit In effect, the dots "pipe" the light from the transparent sheet and the matrix is adjusted such that the density of the dots varies across the sheet to even out the illumination.